Union Pacific , the largest U.S. freight railroad operator, is exploring a possible acquisition of Norfolk Southern to create a $200 billion coast-to-coast rail network, a person familiar with the matter said.

Norfolk Southern, The Wall Street Journal reported Thursday, in a deal that would shake up the railroad business in America.

Merger talk is swirling around Union Pacific Corp. and Norfolk Southern Corp., in a deal that could create a railroad mega-carrier and a huge transcontinental network spanning the U.S.